Plain old telephone service, which has powered voice communications for more than a century, has all but disappeared from everyday office use in favor of IP-based phones. That said, the trusty analog phone line hasn't completely vanished from enterprise use. More than 15 million switched access lines were still in use as of June 2025, according to the Federal Communications Commission (FCC), largely for operational technologies that enterprises often rely on. Common use-case examples include:
Fire and security systems that dial into a monitoring center
Elevator emergency phones required by building codes.
Access control systems and intercoms.
Building management systems.
Fax and other analog specialty devices that never moved to IP.
POTS retirement is only half the equation. Many organizations also still have voice services that depend on the same copper plant that carriers seek to retire. This includes analog business lines, primary rate interface (PRI) or other time division multiplexer trunks that connect into a PBX or contact-center platform. So while desk phones may already be IP on the LAN, the trunks and analog tails that feed the building to the public switched telephone network (PSTN) often are not.
PSTN carriers are escalating their efforts to decommission that aging plant in favor of modern alternatives. The FCC's 2026 Network and Services Modernization Order, as part of the "Build America Agenda," allows carriers to retire these systems with less red tape than ever before, giving customers as few as 90 days' notice. This means enterprises have to migrate quickly, with little time to budget the work, stay within government and 911 requirements and keep life-safety and voice services running while the copper plant goes away.
How to quantify the ROI of a POTS migration
Determining the ROI when swapping out a copper line depends on the circuit's purpose and the business risk it carries. Replacing a POTS line for an elevator phone is not the same case as replacing a PRI into a contact center platform. The costs differ, and so does the return.
A defensible POTS retirement business case, therefore, goes past the new provider's monthly price and the one-time cutover fee. It also has to include avoided risk and, where calling or the contact center actually leaves the retiring plant, gains in employee productivity and contact center agility. Factors to consider include the following:
Direct cost to replace. This is the part of the quantification process where you compare what you pay today for analog lines, PRI and other TDM trunks, plus the PBX or gateway maintenance those circuits keep alive, against the cost of analog-replacement service or appliances and SIP or cloud telephony for remaining voice.
Then you must include one-time design and implementation costs, including site surveys, phone number porting, parallel runs and vendor on-site visits. If the same migration project also replaces an on-premises contact center platform, include that subscription and cutover cost here. Note that a contact center as-a-service cutover is not the cost model for every POTS circuit. Most analog lines never touch the contact center, so keep this comparison on prices you can already quote.
Risk and timing. In situations where carriers are actively pushing customers off copper plant, any delay can cost the enterprise real money and create outage risks once the plant is decommissioned. Rates on leftover circuits rise, repairs become slower and new orders or changes are often frozen before the retirement notice arrives.
Operating metrics. Productivity and contact center agility belong in the ROI calculation only if calling or the contact center actually moves off the copper plant. Additionally, migrating to a cloud phone system can cut time spent on adds, moves and specialized PBX upkeep. Moving off a legacy PRI or an old on-premises contact center can make queues and capacity easier to change. Alternatively, replacing an elevator phone or fire panel does not make employees faster at their jobs, so leave those circuits out of the productivity calculation.
Proactively managing the migration
The day your carrier sends you a decommissioning notice is often not enough time to thoroughly discover what systems and processes still depend on copper. That is why the migration plan starts with an inventory before the carrier ever reaches out. Now is the time to pull and review the bills. Then walk the sites so you know what is actually connected to each circuit.
The day your carrier sends you a decommissioning notice is often not enough time to thoroughly discover what systems and processes still depend on copper.
Note the carrier on the circuit and the vendor that owns the device or system it feeds. Analog life-safety gear still needs something that operates like a standard phone line. PRI and the rest of the voice traffic usually move to SIP or cloud telephony. That is why one vendor may not cover the whole job.
Be sure the fire, elevator and alarm contractors accept the analog design before you order anything. Then use another vendor to bring up SIP or unified communications as a service (UCaaS) in parallel, test 911 and the monitoring circuits. Only port numbers and disconnect the copper once both paths check out.
Compliance, E911 and resilience
POTS retirement doesn't free enterprises from the rules and regulations attached to the purpose of the legacy lines. All OT systems, including fire, elevator and alarm paths, must still adhere to code. Any replacement technologies must be able to "seize" the line, dial outbound and survive power outages with the same resiliency as a copper plant did.
Voice that moves to SIP or UCaaS has a different 911 problem. The number is no longer tied to a physical pair in the building. That means the provider must deliver the right dispatchable location and keep 911 available if the office internet drops. Be sure the design includes the right physical address on every number and a backup path if the office internet fails. Complete a documented 911 test before decommissioning the copper. Neither path should depend on building broadband alone.
Getting a plan in place before POTS disappears
Carriers will retire the copper on their schedule, not yours. Now is the time to find every leftover POTS circuit and TDM trunk before that notice inevitably arrives. Plan to fund analog replacements and the SIP or UCaaS migration for the ROI each one actually produces. Finally, leave the old lines in place until 911 and the monitoring paths pass a real test. Do that, and the migration stays a planned modernization project instead of an emergency cutover that blows the budget and puts life safety at risk.
Andrew Froehlich is founder of InfraMomentum, an enterprise IT research and analyst firm, and president of West Gate Networks, an IT consulting company. He has been involved in enterprise IT for more than 20 years.
